1. Field of the Invention
The present invention relates to an induction heating roller apparatus, and more particularly to an induction heating roller apparatus of the type in which a support rod supporting an induction heating mechanism is inserted into drive shafts provided at both ends of a roller body.
2. Description of the Related Art
A known this type of the apparatus is an induction heating roller apparatus constructed such that drive shafts are integrally formed at both ends of a hollow roller body, the drive shafts are rotatably supported on a machine frame with bearings interposed therebetween, an induction heating mechanism with an induction coil is disposed within the roller body while being supported by a support rod, and the support rod is inserted into the drive shafts, and the support rod is supported on the drive shafts with the aid of the rolling bearings, whereby the induction heating mechanism is supported in a suspending fashion within the roller body,
The induction heating roller apparatus is constructed as shown in FIG. 3. In the figure, reference numeral 1 designates a rotatable, hollow cylindrical roller body 1, both ends of the roller body 1 are integrally coupled with hollow drive shafts 2 via journals 3. The drive shafts 2 are rotatably supported on a fixed machine frame 5 with the aid of bearings 4 located outside. When the drive shafts 2 are rotated by a proper drive source (e.g., a motor), the roller body 1 is rotated.
An induction heating mechanism 8, which is formed with an iron core 6 and an induction coil 7 wound on the iron core, is disposed within the roller body 1. The induction heating mechanism 8 is supported at both ends by a support rod 9. The support rod 9 is supported on the drive shafts 2 by means of rolling bearings 10. With this structure, the induction heating mechanism 8 is supported in a suspending fashion within the roller body 1. Reference numeral 11 designates a lead wire led out of the induction coil 7. The lead wire 11 passes through the induction heating mechanism 8 and connects to an AC power supply for magnetic excitation, which is located outside.
Reference numeral 12 indicates a turning-block bar 12 integrally formed with the support rod 9. Reference numeral 13 is a stopper against which the turning-block bar 12 will hit. When as described above, the drive shafts 2 is rotated by the external drive source, it often takes place that the rotational force of the drive shafts 2, although it is a less magnitude, is transmitted to the support rod 9 through rotational resistance of the rolling bearings 10. If the support rod 9 and the induction heating mechanism 8 are greatly turned by the rotational force, the lead wire 11 will be disconnected in an extreme case. Such turn of the support rod 9 is prevented by the combination of the turning-block bar 12 and the stopper 13 which will hit against the former prevent.
In the structure, the rolling bearings 10 supporting the support rod 9 will often suffer wear, scorching or the like, and will be subjected to repeated stress, possibly being fatigue broken. In the rolling bearings 10 suffering from such undesired phenomenon and fatigue breakage, the rolling bearings 10 do not work normally, so that the rotational resistance of them greatly increases. For this reason, a little rotational torque, which is transmitted when the rolling bearings are normal, becomes large and is transmitted to the support rod 9.
The great rotational torque transmitted damages the turning-block bar 12 and the stopper 13, and the support rod 9 and hence, the induction heating mechanism 8 are rotated. As a result, the lead wire 11 is disconnected. Such a mechanical trouble, if occurs, cannot be cured by merely replacing the rolling bearings 10 with a new one. To completely cure it, it is necessary to disassemble the roller body 1 and to additionally repair the winding of the induction coil 7.
Another solving means to solve the problem was proposed and matured to the patent (see Japanese patent No. 2616798). The patent uses a torque detector for detecting the rotational torque transmitted from the drive shafts 2 to the support rod 9. When the torque detector detects an increase of the torque in excess of a predetermined torque value, it outputs a signal, and the drive shafts 2 are stopped in rotation in response to the output signal. In this way, the patent succeeds in avoiding the undesired rotation of the support rod 9 caused by the trouble of the rolling bearings 10.
The patent is ineffective for the roller body 1 of large weight in solving the above-mentioned problem. That is, when the torque detector detects a machinery trouble of the rolling bearing 10, and the power supply to the drive source and the drive shafts 2 is responsively turned off. However, the drive shafts will continue their turn because of the inertia, and be stopped after certain time elapses. If the rolling bearings 10 are greatly damaged and their rotational resistance considerably increases, the support rod 9 is greatly turned and the lead wire 11 will be disconnected. And the induction heating mechanism 8, which is not originally designed so as to rotate, is also turned and damaged. Further, the torque detector will be damaged.
Accordingly, an object of the present invention is to provide an induction heating roller apparatus in which, when a mechanical trouble occurs in the rolling bearings for the support rod supporting the induction heating mechanism and do not work normally, and the trouble is detected and a drive source for the drive shaft is stopped, the apparatus delays the transmission of a rotation of the support rod by the co-rotation, which results from a rotational torque transmitted from the drive shafts to the support rod by an inertia rotation of the drive shafts which continues till the drive shafts are completely stopped.
To achieve the above object, there is provided an induction heating roller apparatus in which the support rod is supported on the drive shafts with the aid of the rolling bearings, and the induction heating mechanism is supported in a suspending fashion within the roller body. In the present invention, the induction heating roller apparatus comprises sliding bearings being disposed between the drive shafts and the rolling bearings or between the support rod and the rolling bearings.
A trouble occurs in the rolling bearing and it does not work well in a rotation. In an initial stage of the trouble, the rolling bearing is not yet broken. However, a rotational torque will be gradually transmitted from the drive shafts to the support rod through the rolling bearing. When the rotational torque reaches such a predetermined value as not to damage the rolling bearing, a drive source of the drive shafts is stopped. Accordingly, the drive shafts still continue their rotation by the inertia. If the rolling bearing is damaged during this inertial rotation, a large rotational torque will be transmitted from the drive shafts to the support rod through the rolling bearings.
At this time, the drive shafts slip relative to the support rod because of the presence of the sliding bearings. Therefore, it never happens that the support rod and the induction heating mechanism co-rotate greatly, although the inertial rotation of the drive shafts continues. The operation of the sliding bearings may be limited, in its time duration, to within the inertia rotation of the drive shafts. Accordingly, those of compact size may be used and arranged.